Since A. Payen named cellulose for natural fiber, cellulose research has been carried out for about 150 years. However, there are still several basic problems which should be solved : biosynthesis and biodegradation, crystal structure, mercelization mechanism, chemical reactivity, structure-function relationship.Recently, we have succeeded in the first chemical synthesis of cellulose both by stepwise method and by the ring-opening polymerization of glucose orthoester. These synthetic methods enables us to obtain the high-regioselectively substituted cellulose derivatives which can used for the solution of the above several basic problems. In the present investigation, We succeeded in the preparation of 6 regiospecifically methylated celluloses in the possible 7 methyl celluloses. Based on the spectroscopic data of these synthetic methyl celluloses, we established the determination method for the substituent distribution of methyl celluloses. As the results of carboxymethylation and methylation of celluose, we found the new findings about the reactivity of three hydroxyl groups in cellulose molecule. These results suggest new possible effects of inter- and intramolecule hydrogen bondings on the reactivity of three hydroxyl groups.